Organized code is easier to read/understand code. When coding you should always keep it as tidy as possible in case someone else (or even you) has to revisit it down the line. Smashing Magazine gathered the best tools to help you clean up your krufty code in various programming languages.
CSS Beautifier looks to be the best CSS optimizer mentioned by Smashing Magazine. You have complete control over the formatting of your style code including the ability to add a new line, space, tab or nothing after pretty much any CSS property. The best feature has got to be the Alphabetizer which will let you sort properties within a selector or the selectors themselves. Be careful with the last options because changing the order of your CSS selectors could change the way your CSS behaves on a site. Order is important in a cascading stylesheet.
Obviously these two are the tips of the iceberg as Smashing Magazine has more tools for other languages. These two struck me as the most useful to a web developer and that is why they have made it in to my bookmarks of web goodies.